1. Field of the Invention
The invention relates to a joint for structural members, such as floor panels.
2. Description of Related Art
A joint for floor panels is for instance disclosed in EP 0 098 162 B 1. In case of this known, so-called "glue-free" joint, the adjacent circumferential edges of the panels are joined by a groove and tongue joint. There, the lower groove cheek of the one panel facing the contact face is extended beyond the vertical parting plane and comprises a locking projection at its end portion, said locking projection immersing in a corresponding recess of the tongue of the other floor panel. In order to facilitate the laying of the panels, the joint in the engaging portion of the extended groove cheek with the tongue is performed with play so that displacing of the panel along the longitudinal edges is rendered possible.
W097/47834 A-1 shows a generic joint in which, similar to the solution described above, the lower groove cheek of a floor panel is extended beyond the vertical parting plane and is provided with a projection which engages with a corresponding clamping recess of the tongue. Contrary to the solution initially described, the engagement between the extended groove cheek and the corresponding recess of the tongue is performed such that a force is exerted by this locking which presses the two floor panels towards each other perpendicular to the vertical plane.
In both solutions described above, the groove and tongue joint has a double function. The groove and tongue joint on the one hand ensures the accurately fitting positioning of the two floor panels relative to each other so that no gaps and projections occur and the required laying quality is guaranteed. The second function consists in ensuring this predetermined relative position by the non-positive or positive locking between the extended groove cheek and the tongue even in the case of strain on the floor or of temperature and moisture fluctuations.
It is a problem with the known solutions that the extended groove cheek has to be resiliently deformed to perform the engagement between the locking elements. In the case of unfavourable conditions, for instance with excessive strain of the resilient lower groove cheek or in the case of swelling due to moisture and the influence of temperature, cracks may occur in the contact area of the lower groove cheek with the pertinent floor panel so that the groove cheek can no longer fulfil the locking function described before. In addition, the quality of the fitting of the groove and tongue joint is aggravated in the case of such cracks occurring in the contact area, so that the accuracy required for correct floor laying is no longer guaranteed.